JPH05179192A - Formation of coating film - Google Patents

Abstract

PURPOSE:To form a coating film markedly improved in appearance, film properties, weather resistance, etc., on a difficulty coatable plastics by applying a coating material prepared by mixing of modifying a specified acrylic copolymer with a chlorinated polyolefin. CONSTITUTION:A difficulty coatable plastics is coated with a coating material prepared by mixing or modifying 100 pts.wt. acrylic copolymer (A) obtained by copolymerizing 3-40wt.% sec. hydroxy-containing (meth)acrylic ester of formula I, II or III with 0.1-10wt.% vinyl monomer containing at least one group selected from among carboxyl, sulfonic and phosphoric groups, 30-96.9wt.% alkyl methacrylate with 1-4C alkyl and another copolymerizable monomer and having a hydroxyl value of 10-80mgKOH/g, an acid value of 1-30mgKOH/g and a glass transition temperature of 20-80 deg.C with 3-40 pts.wt. chlorinated polyolefin of a chlorine content of 15-50%.

Description

Detailed Description of the Invention

[0001]

[Field of Industrial Application] The present invention directly coats an acrylic paint excellent in long-term stability, coating workability, adhesion, etc. on a hard-to-paint plastic to significantly improve the appearance, coating film performance, weather resistance, etc. The present invention relates to a method for forming a coating film to be improved. Here, the difficult-to-coat plastics refer to plastics such as polyolefin resins such as polyethylene and polypropylene, nylon resins, etc., which have poor adhesion of the coating film and are difficult to coat.

[0002]

2. Description of the Related Art In recent years, the expansion of plastic materials into industrial materials is expanding more and more, and among them, polyolefin resins such as polyethylene and polypropylene are used for automobiles due to their features such as moldability, weight reduction, low cost and recyclability. It is expected that the demand will increase significantly. However, since polyolefin resins generally have high crystallinity and low polarity, paints, printing inks, adhesives, etc. are unlikely to adhere to them, so that some kind of pretreatment has always been required before coating.

Specific examples of the pretreatment means include physical treatments such as polishing, chemical treatments such as chromic acid mixture and solvent, and treatments by plasma and corona discharge. Further, it has been proposed to apply a chlorinated product of a polyolefin resin as a primer, but these methods are not only insufficient in coating film performance and weather resistance, or the adhesion is deteriorated over time, and However, there are problems such as high costs.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for forming a coating film which is excellent in various performances and which does not require a pretreatment or a primer coating process for a plastic which is difficult to coat. There is.

[0005]

The present invention provides a method for forming a coating film in which at least one layer of acrylic paint is applied to a surface to be coated, wherein the acrylic paint comprises (a) the following general formulas (I) and (I
A vinyl-based monomer containing 3 to 40% by weight of a (meth) acrylic acid ester containing a secondary hydroxyl group represented by I) or (III) and (b) at least one of a carboxyl group, a sulfonic acid group and a phosphoric acid group. 0.1 to 10% by weight of monomer, (c)
A hydroxyl value obtained by copolymerizing 30 to 96.9% by weight of a methacrylic acid alkyl ester containing an alkyl group having 1 to 4 carbon atoms and (d) another copolymerizable monomer is 10
To 80 mgKOH / g, acid value 1 to 30 mgKOH / g, and glass transition temperature of 20 to 80 ° C., and chlorinated polyolefin chlorinated in a chlorine content range of 15 to 50. A coating film forming method is characterized in that (B) is applied with an acrylic paint mixed or modified in an amount of 3 to 40% by weight with respect to 100 parts by weight of the acrylic copolymer (A).

[Chemical 4]

[Chemical 5]

[Chemical 6]

The present invention will be described in detail below. First, the (meth) acrylic acid ester (a) containing a secondary hydroxyl group represented by the general formulas (I), (II) and (III) is used for improving the coating performance, weather resistance and the like of the present invention. It is a particularly effective component for improving the interlayer adhesion when a multilayer coating is formed by coating a thermosetting coating on the coating formed by coating the acrylic coating of the present invention. It is an ingredient.

Specific examples of these compounds include 2-
Hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxypentyl (meth) acrylate, polypropylene glycol methacrylate (NOF CORPORATION Plenmer PP-100).
0), an oligomer of 2-hydroxypropyl acrylate (HP-20, Nippon Shokubai Kagaku Co., Ltd.) and the like, each of which may be used alone or in combination.

The amount of the (meth) acrylic acid ester having a secondary hydroxyl group used is in the range of 3 to 40% by weight. If it is less than 3%, the effect of improving the performance is not sufficient, and 4
If it exceeds 0% by weight, the viscosity of the copolymer becomes too high, the adhesion to the surface to be coated, the appearance of the coating film, the water resistance, etc. are deteriorated, which is not preferable.

Next, among vinyl monomers (b) containing at least one of a carboxyl group, a sulfonic acid group and a phosphoric acid group, the carboxyl group-containing monomer is a monocarboxylic acid such as (meth) acrylic acid, Itaconic acid, maleic acid,
Examples thereof include fumaric acid, crotonic acid, trimellitic acid and monoesters thereof. Also sulfoethyl (meth)
Also included are sulfonic acid group-containing monomers such as acrylate and vinylbenzene sulfonic acid, and phosphoric acid group-containing monomers such as methacrylooxyethyl phenyl acid phosphate.

These monomers (b) have the effect of improving the adhesiveness of the acrylic paint used in the present invention, and are also useful as a reaction catalyst when a crosslinking agent is used.
It is used in the range of 10% by weight. If it is less than 0.1%, the above effect is not sufficient, and if it exceeds 10% by weight, the viscosity of the copolymer becomes too high, and the appearance, water resistance and the like of the coating film are deteriorated.

The (c) alkyl methacrylic acid alkyl ester containing an alkyl group having 1 to 4 carbon atoms is a component effective for improving coating workability, drying property, hardness, solvent resistance and weather resistance. Used in the range of ˜96.9% by weight. Specifically, methyl methacrylate, ethyl methacrylate,
Examples thereof include n-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, etc., which may be used alone or in combination.

The acrylic copolymer (A) which constitutes the coating material of the present invention includes, in addition to the compounds (a), (b) and (c) described above, other monomers (d) copolymerizable therewith. ) May be contained.

Specific examples of the other copolymerizable monomer (d) include metal acrylate, ethyl acrylate, and n.
-Acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms such as butyl acrylate; hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isobornyl ( (Meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate having (meth) acrylic acid ester having an alkyl group having 5 or more carbon atoms; styrene derivatives such as styrene, α-methylstyrene and vinyltoluene Polymerizable unsaturated nitriles such as (meth) acrylonitrile; Vinyl esters such as vinyl acetate and vinyl propionate; Alkoxy such as N-methoxymethyl (meth) acrylamide and N-butoxymethyl (meth) acrylamide Conversion amides; glycidyl (meth)
Epoxy group-containing monomers such as acrylate and methylglycidyl (meth) acrylate; basic monomers such as dimethylaminoethyl (meth) acrylate and vinylpyridine; 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl ( A hydroxyl group-containing monomer such as (meth) acrylate may be used alone or in combination according to the purpose and required performance.

The acrylic copolymer (A) of the present invention can be easily produced by a known method. That is, the monomer mixture of the present invention is added in the presence of a radical polymerization initiator to 60
It can be obtained by continuing the reaction for 6 to 12 hours at a reaction temperature of ˜180 ° C., more preferably 75 to 100 ° C. The polymerization method is also not particularly limited, but solution polymerization is advantageous in terms of productivity and performance. As the organic solvent, aromatic hydrocarbons such as toluene and xylene, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and esters such as ethyl acetate and n-butyl acetate are used. It is preferable to use toluene, xylene, or the like, which has good solubility of the modified polyolefin (B).

The number average molecular weight of the acrylic copolymer (A) is not particularly limited, but preferably 5,000 to 500.
The range is 00. The glass transition temperature is 20-80.
Limited to the range of ° C. If the temperature is lower than 20 ° C, the coating film becomes soft, so that the hardness, solvent resistance, weather resistance and the like are deteriorated, and if the temperature exceeds 80 ° C, the coating film becomes brittle, which are not preferable.

The hydroxyl value of the acrylic copolymer (A) is 1
Limited to 0-80 mg KOH / g. If the acrylic copolymer is within this hydroxyl value range, a hydroxyl group-containing monomer other than the secondary hydroxyl group-containing monomer of the present invention (described in the other monomer (d) section) will impair the characteristics of the present invention. It can also be used together within the range that does not exist. If it is less than 10 mgKOH / g, the effect of improving coating performance and weather resistance is not sufficient and 80 mgK
If it exceeds OH / g, the adhesion, appearance, water resistance, etc. of the surface to be coated are deteriorated, which is not preferable. Moreover, the acid value is 1 to 3.
Limited to 0 mg KOH / g. If it is less than 1 mgKOH / g, the adhesion improvement and the catalytic effect in the system using the cross-linking agent will be insufficient, and if it exceeds 30 mg KOH / g, the stability of the coating in the system using the cross-linking agent, the appearance of the coating film and the water resistance will be poor. Both of them are not preferable because they decrease.

The chlorinated polyolefin (B) chlorinated with a chlorine content in the range of 15 to 50% is an effective component for improving the adhesiveness with the difficult-to-paint plastic, and the acrylic copolymer (A). The chlorinated polyolefin (B) is mixed with 100 parts by weight in the range of 3 to 40% by weight or modified by heat treatment. Chlorinated polyolefin (B) is 3
If it is less than 40%, the adhesion to the surface to be coated is not sufficient,
If it exceeds the range, the coating film performance, weather resistance and the like are deteriorated, which are not preferable. If the chlorine content of the chlorinated polyolefin is less than 15%, the compatibility with the acrylic copolymer (A) is poor, and if it exceeds 50%, the adhesion to the surface to be coated is reduced, which is not preferable.

The acrylic coating composition of the present invention can improve the coating performance such as solvent resistance and water resistance and weather resistance by mixing a melamine resin and a polyisocyanate as a cross-linking agent component. Specific examples of the melamine resin that can be used include n-butylated melamine resin and methylated melamine resin.

The polyisocyanate may be a polyisocyanate compound having a free isocyanate group or may be a blocked one. Polyisocyanates having free isocyanate groups include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate, cyclic aliphatic diisocyanates such as xylylene diisocyanate and isophorone diisocyanate, and aromatic diisocyanates such as tolylene diisocyanate. Examples thereof include organic diisocyanates themselves, or adducts of excess amounts of these organic diisocyanates with polyhydric alcohols, water and the like, polymers of the above organic diisocyanates, and isocyanate burettes.

However, the mixing amount of these cross-linking agents is quantitatively limited in order to maintain good adhesion to the plastic which is difficult to coat. That is, acrylic copolymer (A) 1
It is limited to a range not exceeding 20 parts by weight with respect to 00 parts by weight, and a ratio of hydroxyl group / isocyanate group equivalent ratio in the acrylic copolymer = 1 / 0.1 to 1/1.

The acrylic paint of the present invention is not limited to acrylic pastes such as aluminum paste, brightening agents such as mica, coloring agents such as titanium oxide, carbon black and quinacridone, alkyd resins, epoxy resins, fibrous resins and petroleum resins. The resin, the surface conditioner, the ultraviolet absorber, the antioxidant, the curing catalyst, the auxiliary additive such as the pigment settling agent, etc. are selected as necessary and added by a general compounding method.

The method of forming a coating film using the acrylic paint of the present invention is carried out by a known and conventional method. Generally, after diluting with a suitable organic solvent, dry film thickness is 20 ~ 80μ
It is spray-painted with a spray gun within a certain range.
The coating film coated with the acrylic coating material of the present invention, when at least one layer of the thermosetting coating material is coated thereon, is extremely excellent in interlayer adhesion with the thermosetting coating film, so that it can be used for a long period of time. It is possible to form a multi-layer coating having excellent performance.

[0023]

EFFECTS OF THE INVENTION According to the present invention, the appearance of a plastic which is difficult to paint is improved without pretreatment or primer coating.
Not only is it possible to form a coating film having excellent coating film performance and weather resistance, but it is also possible to form a multilayer coating film having excellent interlayer adhesion, which contributes to the expansion and development of hard-to-paint plastics.

[0024]

EXAMPLES The present invention will be described below with reference to examples. In the text, "part" and "%" represent parts by weight and% by weight, respectively. (Production Example of Acrylic Copolymer) In a four-necked flask equipped with a condenser, a thermometer, a dropping funnel and a stirrer, 60 parts of toluene and a chlorinated polyolefin having a chlorine content of 27% (Toyo Kasei Co., Ltd.) Made hard Ren-14LLB) 3
40 parts of 0% toluene solution was charged and the inner temperature of the flask was adjusted to 95.
The temperature was raised to ° C. Then 33 parts of methyl methacrylate, i
-Butyl methacrylate 40 parts, styrene 5 parts, 2-hydroxypropyl acrylate 9 parts, methacrylic acid 1
Part, benzoyl peroxide 1 part, and azobisisobutyronitrile 1.5 parts were added dropwise over 3 hours. After 1 hour and 2 hours, 0.3 parts of azobisisobutyronitrile was added, and after 2 hours, 12 parts of toluene was added.
50 parts of heating residue, number average molecular weight of 20
000, acrylic copolymer A with a glass transition temperature of 60 ° C
-1 was obtained. Further, by changing the amount of polymerization initiator, the monomer composition, the amount of chlorinated polyolefin, etc., A-2 to A shown in Table 1
-7 was obtained.

[0025]

[Table 1]

(Production Example of Thermosetting Topcoat Paint) 50 parts of xylene and 20 parts of n-butyl acetate were charged into a four-necked flask equipped with a condenser, a thermometer, a dropping funnel and a stirrer, and the temperature was raised to 120 ° C. The temperature was raised. Then 10 parts of styrene,
Methyl methacrylate 10 parts, n-butyl methacrylate 40 parts, 2-ethylhexyl methacrylate 20 parts,
A mixed solution of 18.5 parts of 2-hydroxyethyl methacrylate, 1.5 parts of methacrylic acid and 3 parts of tert-butyl peroxyoctoate was added dropwise over 3 hours. 1
After 2 hours, 0.2 part of tert-butyl peroxyoctoate was added, and after 2 hours, 30 parts of xylene was added.
And then cooled to a glass transition temperature of 32 ° C., a hydroxyl value of 80 mg KOH / g, an acid value of 9 mg.
A KOH / g acrylic curable top coat acrylic copolymer N-1 was obtained.

Examples 1 to 7 and Comparative Examples 1 to 9 The acrylic copolymers A-1 to A-7 and the thermosetting acryl copolymer N-1 for topcoat were blended as shown in Table 2. Then, the acrylic paints P-1 to P-12 are adjusted, and the polypropylene resin B which is a difficult-to-paint plastic.
C-3B (product of Mitsubishi Petrochemical Co., Ltd.) was coated and heated and dried to evaluate adhesion, appearance, coating film performance, weather resistance and the like. In some cases, a thermosetting type topcoat coating film was further formed on the coating film to evaluate the interlayer adhesion and the like. The details of the evaluation results are shown in Tables 3 and 4, and by using the acrylic copolymer of the present invention, the adhesion to the surface to be coated and the topcoat coating which were not obtained by the prior art and various coating performances , A coating film with excellent weather resistance could be formed.

[0028]

[Table 2]

In Table 2, * 1 to 8 are as follows. * 1 Toyo Kasei Kogyo Co., Ltd. Hardlen-14 LLB * 2 Toyo Aluminum Co., Ltd. aluminum paste (65% active ingredient) * 3 Mitsui Toatsu Co., Ltd. n-butylated melamine resin (60% active ingredient) * 4 Non-yellowing polyisocyanate manufactured by Nippon Polyurethane Co., Ltd. (NCO content 21.3%) * 5 Acrylic surface conditioner manufactured by Monsanto * 6 UV absorber manufactured by Ciba-Geigy * 7 Light stabilizer manufactured by Sankyo Co., Ltd. * 8 Ford cup No. 1 with a thinner of xylene / butyl acetate = 90/10. 4 was measured at 20 ° C.

[0030]

[Table 3]

[0031]

[Table 4]

In Tables 3 and 4, * 1 to 9 are as follows. * 1 n-Butyled melamine resin manufactured by Mitsui Toatsu Co., Ltd. * 2 Non-yellowing polyisocyanate manufactured by Nippon Polyurethane Co., Ltd. * 3 Acrylic copolymer N-1 was mixed with Coronate HX to prepare a coating material. * 4, 5 Gobang eyes (1 mm interval) → Adhesion rate by peeling cellophane tape. As the coated surface (plastic), polypropylene resin BC-3B manufactured by Mitsubishi Petrochemical Co., Ltd. was used.
. * 6 Mitsubishi Uni (Scratch hardness) * 7 Gauze was impregnated with xylene and the appearance after 16 reciprocating rubbing was visually judged. * 8 It was immersed in warm water at 40 ° C for 10 days, and the appearance after pulling was visually determined. * 9 After 1000 hours of sunshine WOOM, the appearance was visually observed, and the adhesiveness was evaluated by peeling with scotch tape.

Front Page Continuation (72) Inventor Yasuhito Umemura 4-60 Sunadabashi, Higashi-ku, Nagoya, Aichi Prefecture Mitsubishi Rayon Co., Ltd. Product Development Laboratory

Claims (3)

[Claims] 1. A method for forming a coating film in which at least one layer of acrylic paint is applied to the surface to be coated, wherein the acrylic paint is represented by the following general formula (I), (II) or (III): (Meth) acrylic ester 3 containing secondary hydroxyl group
To 40% by weight, (b) 0.1 to 10% by weight of a vinyl-based monomer containing at least one of a carboxyl group, a sulfonic acid group and a phosphoric acid group, and (c) an alkyl group having 1 to 4 carbon atoms. Methacrylic acid alkyl ester containing 30-9
6.9 wt% and (d) a copolymerizable other monomer having a hydroxyl value of 10 to 80 mgKOH / g,
Acid value 1 to 30 mg KOH / g and glass transition temperature 20
The acrylic copolymer (A) having a temperature of up to 80 ° C. and the chlorinated polyolefin (B) chlorinated in a chlorine content range of 15 to 50 relative to 100 parts by weight of the acrylic copolymer (A). A method for forming a coating film, which comprises applying an acrylic paint mixed or modified in an amount of 3 to 40% by weight. [Chemical 1] [Chemical 2] [Chemical 3] 2. A melamine resin as a cross-linking agent is used in an amount of 20% by weight or less based on 100 parts by weight of the acrylic copolymer (A) in preparing an acrylic coating material using the acrylic copolymer (A). The method for forming a coating film according to claim 1, wherein the polyisocyanate is mixed in a range of NCO / OH = 0.1 / 1 to 1/1 in an equivalent ratio with the hydroxyl group-containing monomer in the acrylic copolymer. 3. The method for forming a coating film according to claim 1, wherein at least one thermosetting coating material is applied onto the coating film formed from the acrylic coating material (A) to form a multilayer coating film.